Most robot arms of the prior art are rigid. Rigidity is desired for lifting loads having substantial mass and, it has been tought, for accurate positioning of the arm. Most prior art robot arms rely on motors for accurate movement of arm joints. Usually robot arms are formed by a plurality of rigid links connected by joints with motors changing positions of the links, usually by means of gears attached to the links at the joints. Alternatively, exterior hydraulic pistons and cylinders have been used to change the position of one link relative to another link in much the same way as linkages appearing on other industrial equipment, such as earth moving equipment and farm machinery. The most recent robot arms developed utilize servo controlled stepper motors for precise positioning of arm links.
There is a class of robot applications where a rigid arm is not desired. For example, in home uses a rigid arm could be dangerous, especially where small children are present. In other applications, where the object to be manipulated has very low mass, such as a wafer of the type used in integrated circuit fabrication, a rigid arm is simply not needed and could cause damage to a wafer in the event of a positioning error. Since a rigid arm is not intended to give, a positioning error could cause breakage of the wafer by causing it to bump into a fixed object. There is still another class of robots, which may be classified as toys or theatrical robots, which perform under computer control. These robots do not need rigid arms and might be dangerous if so equipped.
Another object of the invention was to devise a non-rigid or semi-rigid robot arm which could bend or extend on command.